Wednesday, November 7, 2007
261-1
A Comparison between Tropical and Temperate Maize Hybrids Grown in Subtropical Environments of Argentina.
Oscar R. Valentinuz, Facultad de Ciencias Agropecuarias (UNER) - INTA Paraná, Ruta 11 km 12.5, Oro Verde, Argentina, Sergio Uhart, DowAgroSciences-Maizar, Santiago del Estero, Argentina, and Marcelo Metzler, Facultad de Ciencias Agropecuarias (UNER), Oro Verde, Argentina.
Hybrids with tropical germplasm might perform better than temperate hybrids when planting dates are delayed in the North of the Pampas, Argentina. Our objective was to compare growth and yield of tropical maize respect to temperate and tropical x temperate hybrids in order to get a better understanding of the physiological basis of interaction among planting date (P), population density (D) and hybrid (H). Experiments included a temperate (TM), two tropical (TR) and a temperate x tropical (TMxTR) maize hybrids grown under two D (2005/6) and under three P and two D (2006/7). There was a severe drought during 2005/6 and rainfall during 2006/7 was about 1.5 fold greater than that registered in the first campaign, which resulted in similar differences in grain yield (7943 vs. 3239 kg ha-1). In 2005/6, grain yield for TM and TMxTR hybrids was 145% greater than that observed in TR hybrids and differences were mainly associated to kernel number (1915 vs. 725 kernel m-2). There was not DXH interaction. In 2006/7 grain yield response to P was similar for all hybrids. Grain yield for early and intermediate P (7945 kg ha-1) was 14% greater than that for late P. Grain yield for TM and TMxTR hybrids was 24% greater than that observed in tropical hybrids (8438 vs. 6803 kg ha-1). Both, grain yield and kernel number showed a significant PXD interaction. In turn, significant DXH and PXH interactions were observed for grain yield and kernel weight, respectively. Hybrids showed differences in partitioning of biomass to developing ear (EP) in response to population density, while EP was stable in TR, EP increased in TMxTR (20%) and decreased in TM (10%) when D varied from 6 to 8 plants m-2. Our results indicate that TMxTR hybrids perform better than TR hybrids in delayed planting date and that hybrids bearing temperate and tropical germplasm seem to be less sensitive to population density in delayed planting date.